Conventionally, a device that merges captured images to create a panoramic still image being one wide-angle still image is known as an image processing device (e.g., see Patent Document 1). The image processing device described in Patent Document 1 merges a plurality of images obtained by imaging in different orientations from the same point. Specifically, respective coordinate systems of two images are unified using a transformation matrix and then the images are merged. This transformation matrix is calculated using a least-square method.